With the improved life expectancy of most children with cancer, attention has been turned to improving the quality of life of cancer survivors and their family members. It is well-known that family conflict is one of the best familial predictors of childhood behavior problems. There is also recent evidence that children with cancer have higher levels of conflict with their parents than healthy controls, and that family conflict is associated with higher psychological distress in young cancer patients and their caregivers. Yet, little is known about the nature and course of family conflict post-cancer diagnosis and through the treatment process. To develop interventions to reduce the adverse effects of cancer diagnosis and treatment and improve outcomes for cancer patients, their families and their caregivers, it is important to identify the nature and course of conflict within the family and determine whether family conflict is associated with maladjustment in children with cancer and their caregivers. Building on recent conceptual and methodological advances in the field of family research, the proposed research will use a multi-method approach to test a conceptual model of how the stresses inherent in cancer diagnosis and treatment affect family conflict and child and caregiver adjustment. In a short-term prospective longitudinal study, self-report, observational and physiological methods will be used to study families of young children diagnosed with the most common forms of young childhood cancer: acute lymphoblastic leukemia, central nervous system tumors, Wilms tumor and neuroblastoma. The primary aims of the proposed research will be: (1) to describe the course of family conflict across the disease process; (2) to test whether stress occurring during cancer treatment is associated with family conflict across the disease process and whether family conflict increases with increases in stress; (3) to test whether family conflict at the early stages of the disease process predicts the manner in which families deal with the treatment process itself; and (4) to test whether family conflict mediates relations between stress during cancer treatment and adjustment in children with cancer and their caregivers. Competing meditational models relating to parental depression and parental overprotection will also be tested. Positive qualities of the relationship between the child with cancer and their primary caregiver, as well as children's emotion regulation abilities, will be explored as potential resilience factors that buffer children from the negative outcomes. Promising findings can provide direction for prevention and intervention efforts that can have significant impact on the long-term development of children with cancer and their caregivers.